Conventional AC-DC converters, in particular buck PFC AC-DC converters or buck PFCs, employ precise current measurement systems or other comparable, complex schemes. Some examples of conventional AC-DC converters are U.S. Pat. Nos. 6,275,018; 6,381,150; 6,909,266; and 7,391,630; U.S. Patent Pre-Grant Pub. Nos. 2006/0002155 and 2008;0205104; Chattopadhyay et al., “A Predictive Switching Modulator for Current Mode Control of High Power Factor Boost Rectifier,” IEEE Transactions on Power Electronics, Vol. 18, No. 1, Jan. 2003; Zhang et al., “A Digital Power Factor Correction (PFC) Control Strategy Optimized for DSP,” IEEE Transactions on Power Electronics, Vol. 19, No. 6, November 2004; and Zhang et al., “A New Predictive Control Strategy for Power Factor Correction,” 18th Annual IEEE Applied Power Electronics Conference and Exposition, February 2003, vol. 1, pp. 403-409. Yet, none of these references disclose a buck PFC that does not employ a precise current measurement or other comparable, complex system.